Grounding clip for electrical fixtures

BACKGROUND OF THE INVENTION

The present invention relates to grounding apparatus for electrical fixtures and especially such apparatus which affixes directly to the electrical fixture without modification thereof. Hitherto, many different devices have been utilized to provide a grounding path between an electrical fixture and its mounting box. The most conventional approach has been to establish this path with a bonding jumper which requires that a wire be attached to both the electrical fixture and the mounting box for providing an electrical interface therebetween. This approach is very time consuming and even where sufficient time has been allotted for the incorporation of the bonding jumper, it is inadvertently disregarded on occasion to thereby result in a hazardous condition.

Another approach is to establish the grounding path by abutting the mounting yoke of the electrical fixture directly against the mounting box to achieve a metal-to-metal surface contact therebetween. Such a metal-to-metal abutment is not possible in all mounting arrangements between electrical fixtures and mounting boxes and therefore, this approach is limited to particular applications. It is also true, that the contact resistance resulting at such an abutment between surfaces is very susceptible to drastic increases from adverse circumstances and therefore, the reliability of the grounding path established thereby is very low.

Specially configured metallic clips are utilized in some applications to establish the grounding path. Disadvantages accompanying the use of these clips to achieve a low resistance grounding path between the electrical fixtures and the mounting box. One such clip is that disclosed in U.S. Pat. No. 3,432,793 which is fixedly attached to the electrical fixture and exerts a spring bias against the mounting screw. Being fixedly attached, this clip can only be utilized if the electrical fixture is modified, therefore, it increases manufacturing costs appreciably and can not be applied directly to conventional electrical fixtures. Another such clip is that disclosed in my U.S. Pat. No. 3,663,919 which presents a protruding member to be forcibly wedged between the electrical fixture and the mounting box. Although this clip is highly regarded for its intended purpose, once it is installed, the electrical fixture becomes more difficult to remove from the mounting box and thereby may present a problem during maintenance.

SUMMARY OF THE INVENTION

It is therefore a general object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip which minimizes and obviates the disadvantages of the prior art.

It is a specific object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip which may be applied directly to the electrical fixture without modification thereof.

It is a more specific object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip which in no way inhibits the removal of the electrical fixture from the mounting box.

It is another object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip which exerts a continual contact pressure against both the electrical fixture and the mounting screw securing the fixture to the box.

It is still another object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip which includes a screw-receiving means of self-adjusting pitch.

It is a further object of the present invention to provide a grounding path between an electrical fixture and a mounting box with a clip having protrusions which intensify the contact pressure on the electrical fixture.

These objects are accomplished in one form according to the present invention by arranging the members of a U-shaped clip to forcibly grip across the mounting yoke thickness of conventional electrical fixtures. An aperture is disposed through one member of the clip in alignment with a screw-receiving means through the other member. Protrusions are disposed on either member to project into the gap separating the members and serve to facilitate the electrical contact achieved with the mounting yoke. Cooperating cantilever springs are incorporated into the screw receiving means and exert a force against the mounting screw regardless of its pitch variation or the pitch reference established by the fixed threads within the mounting box.

BRIEF DESCRIPTION OF THE DRAWING

The manner in which these and other objects of the invention are achieved will be best understood by reference to the following description, the appended claims, and the FIGS. of the attached drawing wherein:

FIG. 1 is a partial top view of an electrical fixture mounted into a mounting box with the grounding clip of this invention incorporated therebetween;

FIG. 2 is a side view thereof with portions of the mounting box cutaway to illustrate the electrical continuity existing between the ground terminal of the electrical fixture and the mounting yoke thereof.

FIG. 3 is an enlarged partial sectional view thereof, taken substantially along line 3--3 of FIG. 2 to illustrate the self-adjusting pitch feature of the grounding clip and the concentrated contact pressure attained with the protrusions thereof;

FIG. 4 is an enlarged partial sectional view thereof, taken substantially along line 4--4 of FIG. 1 to illustrate the conductive path provided between the electrical fixture and the mounting box by the grounding clip;

FIG. 5 is a top perspective view of the grounding clip;

FIG. 6 is a bottom perspective view thereof; and

FIG. 7 is an enlarged sectional view thereof taken substantially along the line 7--7 of FIG. 6 to illustrate the relative disposition of the screw-receiving means and the protrusions thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawing, and more particularly to FIGS. 1 and 2, there is illustrated an electrical fixture 10 which is secured into a mounting box 12 with a grounding clip 14 disposed therebetween in accordance with this invention. Any suitable electrical fixture 10 could be secured into the mounting box 12 but by way of example, a standard duplex receptacle outlet 16 has been chosen for use in this disclosure. To eliminate the safety hazard which would otherwise exist, the grounding clip 14 provides for the electrical continuity necessary to achieve a grounding path between the outlet 16 and the mounting box 12.

In general configuration, the mounting box 12 is an open ended enclosure, having rectangular sides. The mounting box 12 is fabricated of conductive metal and is electrically grounded by suitable means, such as connection to a water pipe (not shown). A mounting flange 18 is provided on the mounting box 12 and has threaded aperture 20 which engage with mounting screws 22 in securing the outlet 16 to the mounting box 12.

The outlet 16 has a generally compatible configuration to that of the mounting box 12 and includes a body 24 made of suitable insulating material, such as moldable plastic. At the front of the body 24, identical but separate grounded receptacles 26 are disposed. Each receptacle 26 includes a pair of spaced slots 28 associated with internal female contacts (not shown) and a semi-circular opening 30 associated with an internal female grounding contact (not shown). The female contacts mate with the male contacts of a plug and the female grounding contact mates with the male grounding contact on the plug. Screws 32 comprise suitable terminal means for connecting wire conductors to the female contacts and thereby provide for electrically energizing the receptacles 26. A metallic mounting yoke 34 extends across the rear of the body 24 and is affixed thereto by any suitable means, such as folding tabs 36. The mounting yoke 34 is also configured to extend along both sides of the body 24 and project laterally therefrom to each side thereof to form mounting ears 38. An elongated slot 40 is disposed through each mounting ear 38 to permit passage of the mounting screw 22 in alignment with the threaded aperture 20 of the mounting box 12. A grounding screw 42 comprises suitable terminal means for connecting a ground wire to the mounting yoke 34 which in turn is electrically connected by suitable means (not shown) to the female grounding contacts within the receptacles 26.

The grounding clip 14 is made of resilient, conductive material, such as a spring metal strip, in a generally U-shaped configuration which includes an upper plate-like member 44 and a lower plate-like member 46, with reference to and as illustrated in FIGS. 5-7. The members 44 and 46 are connected to each other at an adjacent end of each, and separated by a gap 48 of less magnitude than the thickness of the mounting ear 38. An aperture 50 is formed in the upper member 44 and a screw-receiving means 52 for engaging with the threads of the mounting screw 22 is disposed through the lower member 46, with the longitudinal axes of both the apertures 50 and the screw-receiving means 52 aligned along a common axis A-A. Protrusions 54 extend into the gap 48 from the upper member 44 and the termination of each member 44 or 46 is configured to diverge relative to the other member 44 or 46 in that an inclined tip 56 is disposed on the upper member 44 and a locating flange 58 is disposed on the lower member 46. A spring means 60 of suitable construction, such as cooperating cantilever members 62, is incorporated into the screw receiving means 52 and a rolled tip 64 is disposed at the end of each cantilever member 62

In use the grounding clip 14 is applied to the mounting yoke 34 of the outlet 16 by forcibly directing one of the mounting ears 38 thereof into the gap 48 separating the upper member 44 from the lower member 46. A guided entrance 66 is created by the complementary contours of the inclined tip 56 and the locating flange 58 of the members 44 and 46 respectively, and serves to facilitate the initial insertion of the mounting ear 38 therebetween. The members 44 and 46 are deflected in opposite directions by this insertion which thereby results in contact pressures being exerted against each side of the mounting ear 38. Throughout insertion, the grounding clip 14 is manipulated to align the common axis A--A through the slot 40 in the mounting ear 38. Being disposed within the gap 48, the protrusions 54 present a relatively small contact area against the surface of the mounting ear 38, as illustrated in FIG. 3, and thereby concentrate the contact pressure. The protrusions 54 may have any suitable configuration which depends on the contact pressure to be derived from the deflection attained by the members 44 and 46. Where the protrusions 54 are configured to derive a very large contact pressure, the surface of the mounting ear 38 is scraped thereby to penetrate any nonconductive substances thereon, and results in a decreased electrical contact resistance. When assembled, clip 14 is separably mounted on a mounting ear 38.

The outlet 16 is then placed into the mounting box 12 with the common axis A--A of the grounding clip 14 aligned along the axis of one threaded aperture 20 in the mounting flange 18. The mounting screw 22 is then inserted along the axis of the threaded aperture 20 and turned to secure the outlet 16 in the mounting box 12. As the mounting screw 22 is turned, the threads thereof engage into both the screw-receiving means 52 of the grounding clip 14 and the threaded aperture 20. On the screw-receiving means 52, the rolled tips 64 are configured and disposed to engage between the threads of the mounting screw 22 and thereby establish electrical continuity therebetween, as illustrated in FIG. 3. The spring means 60 is disposed on the screw-receiving means 52 for exerting contact pressure against the threads of the mounting screw 22 in that the cooperating cantilever members 62 thereof are forced to deflect as the mounting screw 22 is inserted therebetween. This contact pressure is exerted through the rolled tips 64 which are forcibly abutted against the threads of the mounting screw 22 and therefore, a decreased electrical contact resistance is accomplished between the grounding clip 14 and the mounting screw 22. Due to the deflectable nature of the cantilever members 62, the screw-receiving means 52 is also self-adjusting the pitch variations between threads on the mounting screw 22 and to fixed pitch references established by the threaded apertures 20 in the mounting box 12. Although a plurality of cantilever members 62 are shown, where desired the spring means 60 could be arranged from a single cantilever member.

The grounding path through which electrical continuity is established between the electrical fixture 10 and the mounting box 12 is illustrated by the dotted line in FIG. 4. At the mounting ear 38, the protrusions 54 are forced to bear against the surface thereof and thereby establish a low resistance interface therebetween. Since the grounding clip 14 is made of conductive material and the protrusions 54 are an integral portion thereof, electrical continuity exists from the protrusions 54 into the upper member 44 and through to the rolled tips 64 on the cantilever members 62 of the lower member 46. The rolled tips 64 are forced to bear against the threads of the mounting screw 22 and thereby a low resistance interface is established therebetween. Within the threaded aperture 20 of the mounting box 12, the engaging threads of the mounting screw 22 establish a low resistance interface which is retained under a contact pressure by the forces required to secure the outlet 16 into the mounting box 12.

It should be readily appreciated by those skilled in this art that the clip embodied by this invention may be applied directly to an electrical fixture without the modification thereof and utilized to accomplish a reliable grounding path between the electrical fixture and a mounting box. Also, the clip exerts continual contact pressure on the electrical interfaces without inhibiting the removal of the electrical fixture from the mounting box and protrusions are disposed on the clip to intensify the contact pressure exerted against the electrical fixture. Furthermore, the screw-receiving means of the clip is self-adjusting to the pitch variations between the threads of the mounting screw and to fixed pitch references of the threads within the box.

It should be understood that the present disclosure has been made only by way of example and that numerous changes in details of construction and the combination or arrangement of parts may be resorted to without departing from the true spirit and the scope of the invention, and therefore the present disclosure should be construed as illustrative rather than limiting.